Physicians involved in therapy in general and interventional cardiology and interventional radiology in particular have been attempting to find a way to deal with occluded (so called “stenotic”) coronary arteries (among other blood vessels, various tubular conduits and similar structures). Additionally, the vessel diameter, as often measured using electronic calipers (‘imaging’ mode), and the frequency shift (‘Doppler’ mode) are of prime importance in determining the mean flow rate through a vessel and both must be accurately known. Unfortunately, methods of obtaining luminal dimensions are different based on the type of inquiry; the physicians interested in interventional treatment of stenosis have approached the problem differently than those interested in determining mean flow rate through a vessel.
Interventional radiologists interested in treatment of stenosis have focused attention principally on the topology of the stenosis almost to the exclusion of other important factors. Of principal importance is the identification of stent length as a risk factor for restenosis. The usual method of choosing stent size relies on visual estimation from the angiogram. Like many practitioners interested in this area the goal has been to assess the value of an objective means of determining stent length. In one instance, a calibrated guide wire (sold under the trademark ATW® Marker Wire; Cordis Corporation) is used as a measurement tool. J. P. Reilly et al. Use of ATW Marker Wire to Guide Choice of Stent Length, Am J Cardiol 2001; 88 (suppl 5A).
The theory behind this and other studies is that choice of appropriate endoluminal revascularization device (e.g., balloon angioplasty, atherectomy, laser recanalization, stents, etc) is a function of stenosis topology. Though excessive length of endoluminal revascularization devices can lead to migration and restenosis, a principal limitation of this analysis is that there are equally important risk factors associated with vessel diameter. Many practitioners pay more care in determining appropriate stent length than expanded stent diameter. As a rule of thumb, physicians generally employ a stent that is one to two sizes larger than the estimated lumen diameter. This practice in and of itself can lead to tissue granulation and further vessel damage.
Practitioners interested in hemodynamics or patency of vessels, defined as continued flow through the treated segment, not necessarily the absence of recurrent stenosis, use alternative tools to measure lumen diameter for purposes of determining the extent of flow there through. Most frequently, imaging tests such as CT Scans are used to assist with dimensional calculations. As a result, no apparatus has been developed that allows for accurate in situ measurement of treated or target tissue for purposes of evaluating patency and/or providing interventional prosthesis.
Therefore, there is an existing need for an accurate method of measuring both stenosis topography as well as luminal dimensions so that the precise interventional prosthesis may be employed. In particular, there is a need for a single device that can measure the width and height of a stenosis while also measuring the diameter of lumen at both healthy and stenotic regions.